Regenerative braking system and method

Abstract

A method for recovering energy during braking of a vehicle is provided. The vehicle has at least one rotatable ground engaging member, a generator operatively connected to the at least one rotatable ground engaging member, and at least one energy storage device coupled to the generator. The method has the steps of: determining a speed of the vehicle; determining a desired slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle; and applying a braking torque to the at least one rotatable ground engaging member using the generator based at least in part on the desired slip. A regenerative braking system for a vehicle and a vehicle having such a system are also disclosed.

What is claimed is: 
     
       1. A method for recovering energy during braking of a vehicle, the vehicle having at least one rotatable ground engaging member, a generator operatively connected to the at least one rotatable ground engaging member, and at least one energy storage device coupled to the generator, the method comprising:
 receiving a braking command generated at least in part in response to a braking actuator being actuated; 
 determining a position of the braking actuator; 
 determining a speed of the vehicle; 
 determining a desired slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle; 
 determining a speed of rotation of the at least one rotatable ground engaging member; 
 determining an actual slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle and the speed of rotation of the at least one rotatable ground engaging member; 
 in response to receiving the braking command, applying a braking torque to the at least one rotatable ground engaging member using the generator based at least in part on the desired slip and the position of the braking actuator; and 
 displaying to a driver of the vehicle a graphical representation of a braking performance based at least in part on a difference between the actual slip and the desired slip. 
 
     
     
       2. The method of  claim 1 , further comprising:
 adjusting the braking torque based at least in part on the difference between the desired slip and the actual slip. 
 
     
     
       3. The method of  claim 1 , wherein:
 the braking actuator has a first position where the braking actuator is not actuated and a second position where the braking actuator is actuated; and 
 the braking torque is applied and adjusted when the braking actuator is in the second position. 
 
     
     
       4. The method of  claim 1 , wherein:
 the generator is a motor-generator having a motor mode and a generator mode; 
 the motor-generator applies a propulsive torque to the at least one rotatable ground engaging member when in the motor mode; 
 the motor-generator applies the braking torque to the at least one rotatable ground engaging member when in the generator mode; and 
 the method further comprises:
 switching from the motor mode to the generator mode in response to the braking command being received. 
 
 
     
     
       5. The method of  claim 1 , wherein:
 the at least one rotatable ground engaging member is at least one driving wheel of the vehicle; 
 the vehicle also has at least one non-driving wheel; and 
 determining a speed of the vehicle includes determining a speed of rotation of the at least one non-driving wheel. 
 
     
     
       6. The method of  claim 1 , wherein the desired slip is less than a critical slip of the at least one rotatable ground engaging member. 
     
     
       7. A regenerative braking system for a vehicle comprising:
 a generator adapted to be operatively connected to at least one rotatable ground engaging member of the vehicle; 
 at least one energy storage device coupled to the generator; 
 a control unit connected to the generator for controlling an operation of the generator; and 
 a vehicle speed sensor connected to the control unit to send a signal representative of a speed of the vehicle to the control unit; 
 a wheel speed sensor connected to the control unit to send a signal representative of a speed of rotation of the at least one rotatable ground engaging member to the control unit; 
 the control unit having a permanent storage medium including machine-readable instructions causing, when executed, the control unit to:
 determine a position of the braking actuator based on a signal received from a braking actuator position sensor; 
 determine a desired slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle; 
 determine an actual slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle and the speed of rotation of the at least one rotatable ground engaging member; 
 in response to receiving a braking command generated at least in part in response to the braking actuator being actuated, control the generator to apply a braking torque to the at least one rotatable ground engaging member based at least in part on the desired slip and the position of the braking actuator; and 
 control a display of the vehicle to display to a driver of the vehicle a graphical representation of a braking performance based at least in part on a difference between the actual slip and the desired slip. 
 
 
     
     
       8. The system of  claim 7 ,
 wherein the machine-readable instructions further cause, when executed, the control unit to:
 control the generator to adjust the braking torque based at least in part on the difference between the desired slip and the actual slip. 
 
 
     
     
       9. The system of  claim 7 , wherein:
 the braking actuator has a first position where the braking actuator is not actuated and a second position where the braking actuator is actuated; and 
 the control unit controls the generator to apply and adjust the braking torque when the braking actuator is in the second position. 
 
     
     
       10. The system of  claim 7 , wherein:
 the generator is a motor-generator having a motor mode and a generator mode; 
 the motor-generator being adapted to apply a propulsive torque to the at least one rotatable ground engaging member when in the motor mode; 
 the motor-generator being adapted to apply the braking torque to the at least one rotatable ground engaging member when in the generator mode; and 
 the machine-readable instructions further cause, when executed, the control unit to switch the motor-generator from the motor mode to the generator mode in response to a braking command being received. 
 
     
     
       11. The system of  claim 10 , wherein:
 the vehicle also has an internal combustion engine selectively operatively connected to the at least one rotatable ground engaging member; and 
 the machine-readable instructions further cause, when executed, the control unit to send a signal to a clutch actuator to disengage the engine from the at least one rotatable ground engaging member in response to the braking command being received. 
 
     
     
       12. The system of  claim 7 , wherein:
 the at least one rotatable ground engaging member is at least one driving wheel of the vehicle; 
 the vehicle also has at least one non-driving wheel; and 
 the vehicle speed sensor is a wheel speed sensor connected to the control unit to send a signal representative of a speed of rotation of the at least one non-driving wheel to the control unit. 
 
     
     
       13. The system of  claim 7 , wherein the desired slip is less than a critical slip of the at least one rotatable ground engaging member. 
     
     
       14. A regenerative braking system for a vehicle comprising:
 a generator adapted to be operatively connected to at least one rotatable ground engaging member of the vehicle; 
 at least one energy storage device coupled to the generator; 
 a control unit connected to the generator for controlling an operation of the generator; 
 a display connected to the control unit; 
 a braking actuator position sensor connected to the control unit to send a signal representative of a position of a braking actuator of the vehicle; 
 a vehicle speed sensor connected to the control unit to send a signal representative of a speed of the vehicle to the control unit; and 
 a rotatable ground engaging member speed sensor connected to the control unit to send a signal representative of a speed of rotation of the at least one rotatable ground engaging member; 
 the control unit having a permanent storage medium including machine-readable instructions causing, when executed, the control unit to:
 determine a desired slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle; 
 control the generator to apply a braking torque to the at least one rotatable ground engaging member based at least in part on the position of the braking actuator; 
 determine an actual slip of the at least one rotatable ground engaging member based at least in part on the speed of the vehicle and the speed of rotation of the at least one rotatable ground engaging member; and 
 send instructions to the display device to display to a driver of the vehicle a graphical representation of a braking performance based at least in part on a difference between the actual slip and the desired slip. 
 
 
     
     
       15. The system of  claim 14 , wherein the graphical representation of the braking performance indicates if the actual slip is higher or lower than the desired slip.